Liquid crystal display (LCD) devices usually consist of two-dimensional arrays of thin-film circuit elements (pixels). Each pixel cooperates with liquid-crystal material to either transmit or prevent light travel through a column of liquid crystal material. The physical size of the pixel array is determined by the application.
A two-dimensional (2D) array, for example, can include two sets of conductive lines extending in perpendicular directions. Each line extending in one direction can provide signals to a column of the array; each line extending in another direction can provide signals to a row of the array.
Conventionally, each row-column position in a 2D array includes a pixel that responds to signals on the lines for the pixel's row and column combination. Through one set of parallel lines, illustratively called “data lines,” each pixel receives signals that determine its state. Through the other set of parallel lines, illustratively called “scan lines,” each pixel along a scan line receives a signal that enables the pixel to receive signals from its data line.
In conventional arrays, each scan line provides a periodic scan signal that enables a component in each pixel connected to the scan line to receive a signal from its data line during a brief time interval of each cycle. Therefore, tight synchronization of the scan signals with signals on the data lines is critical to successful array operation. Tight synchronization in turn requires that the driving signals to the data lines be provided with precise timing.
The circuitry driving the data lines is termed the “data scanner.” The circuitry driving the scan lines is termed the “select scanner.”
The arrays are built on substrates, usually of glass or quartz. The pixel arrays require driving and interface circuitry, and in most cases this circuitry is analog rather than digital, making the circuitry capable of delivering or sensing a range of input signals. However, in many applications the video signal originates in digital form and must be converted to analog form to drive the display. Suitable digital-to-analog (DAC) conversion circuitry can be built using well-known techniques in conventional silicon integrated circuits (ICs). These ICs are mounted on or adjacent to the substrate containing the pixel array and a large number of electrical connections are made between the two. The cost of the peripheral drive, interface chips, mounting, and electrical connections to the display can constitute a significant proportion of the overall cost of a system containing the display.